(1) Field of the Invention
This invention relates to a process for the chemical modification of proteins.
The chemical modification of proteins serves two major concerns It permits understanding of the structure and function of proteins as well as changes in these properties. These two aspects, knowledge of the structure and, in particular, of the active sites and changes in their activity, are particularly important in the case of proteins with a catalytic action such as enzymes.
(2) Background Art
The techniques for modifying proteins and the proteinaceous parts of enzymes are very varied:
It is possible to modify one or more amino acid residues specifically at the level of the active site of an enzyme for the purpose of studying (DS. SIGMAN Annu. Rev. Biochem 1975, 44, 899) or modifying (E. T. KAISER Annu. Rev Biochem. 1985, 54, 565) the catalytic activity. Suicide substrates may be classified in this category (WALSH Annu. Rev. Biochem 1984, 53, 493).
A single type of amino acid residue can be modified by a specific reagent. This method, which is described in the book "Chemical reagents for protein modification" (R. L. LUNDBLAD CRC Press, Bacaratan, USA, 1984) enable information to be obtained on the role of the type of residue affected.
Use of reagents which modify the protein for the purpose of its immobilization on a support, for example grafting of acryloyl groups followed by copolymerisation (K. MARTINER Biochem. Biophys. Acta 1977, 485 1) or the preparation of antibody-enzyme conjugates (D. M. BOORSMA J. Immunol Methods 1979, 30, 245)
Preparation of antigens by covalent binding of a small molecule to a protein (K. FLURKEY J. Neuroimmunol. 1985, 8 115).
Preparation of synthetic glycoproteins called neoglycoproteins (C. P. STOWELL Adv. Carb. Chem. Biochem 1980, 37 225).
Alteration of physicochemical properties such as stability or solubility in water or in organic solvents, by random reactions with the various active sites (V. V. MOZHAEV Aur. J. Biochem. 1988, 173 147).
We have now found a new method for the chemical modification of proteins which is very versatile and which permits the introduction of widely differing groups, both for the study of proteins and for the modification of their properties.
This method enables not only free amine groups to be attacked, but also the other protein functional groups with a nucleophilic character such as hydroxyl, thiol, thioether, imidazole or guanidine functional groups.
Another advantage of the method is the possibility of working either in an aqueous medium or in an organic medium depending on the site which it is desired to modify.